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. Author manuscript; available in PMC: 2019 Jul 1.
Published in final edited form as: J Bone Miner Res. 2018 Apr 25;33(7):1362–1375. doi: 10.1002/jbmr.3422

Figure 9. Proposed model depicting the functions of HDAC4 in the mature osteoblast and osteocyte.

Figure 9.

Under basal conditions, HDAC4 in mature osteoblasts and osteocytes inhibits bone resorption and also has an anabolic effect via inhibiting Sost gene and sclerostin protein expression. After continuous PTH treatment, HDAC4 is necessary for maintaining Runx2 expression. Since Runx2 contributes to Sost gene transcription, continuous PTH decreases Sost and sclerostin in the absence of HDAC4. This leads to a combined increase in bone formation and no resorptive effect of PTH in the absence of HDAC4. These actions indicate the function of HDAC4 in maintaining cortical bone mass and its role in the catabolic effects of PTH on cortical bone.